Shiitake mushrooms were originally cultivated on natural oak logs and only grown in Japan but are now available in the United States. These mushrooms are large, black-brown, and have an earthy rich flavor. This fungus is consumed in foods such as stir-fries, soups, and as a meat substitute.

Shiitake contains proteins, fats, carbohydrates, soluble fiber, vitamins (A, B, B12, C, D, niacin), and minerals. Commercial preparations often use the powdered mycelium of the mushroom before the cap and stem grow. This preparation is called Lentinus edodes mycelium extract (LEM). LEM is rich in polysaccharides and lignans.

Shiitake has been taken by mouth for boosting the immune system, decreasing cholesterol levels, and for anti-aging. Lentinan, derived from shiitake (Lentinus edodes), has been injected as an adjunct treatment for cancer and HIV infection, although currently high quality human scientific evidence is lacking for many proposed indications. Purified lentinan is considered a drug in Japan.

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

GRADE *

Laboratory, animal, and human studies of lentinan have shown positive results in cancer patients when used in addition to chemotherapy drugs. Further well-designed clinical trials on all types of cancer are required to confirm these results. Shiitake mushroom extract (SME) used alone did not show benefit in prostate cancer patients in one study. Please check with a medical oncologist and pharmacist before taking any therapies.

C

Based on preliminary study, lentinan could modulate the immune function and reduce the recurrence rate of genital warts. Further well-designed studies are needed to confirm these results. Currently, more proven therapies are recommended.

C

Based on preliminary studies, lentinan may increase CD4 counts and may qualify in future multi-drug studies in HIV patients. Further well-designed studies are needed to confirm these results. Side effects have been reported and more proven therapies are recommended at this time.

C

Currently, there is limited human evidence supporting the role of lentinan and shiitake as an immunomodulator. Additional study is needed in this area.

C

* Key to grades

A: Strong scientific evidence for this useB: Good scientific evidence for this useC: Unclear scientific evidence for this useD: Fair scientific evidence for this use (it may not work)F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory
The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

There is no proven effective medicinal dose for shiitake. Traditionally, 6-16 grams of the whole, dried shiitake mushroom has been ingested daily. It is typically eaten in soups or taken as a decoction (i.e. boiled for 10-20 minutes, cooled, strained, and consumed). A dose of 1-3 grams of Lentinus edodes mycelium (LEM) has been taken two to three times per day. Shiitake-containing capsules have been taken three times daily for six months. A dose of 4 grams of shiitake powder has also been taken daily for 10 weeks.

Injections should only be given by a qualified healthcare provider.

Intranasal application of lentinan has been studied at a dose of 1 milligram per kilogram, used three times at two-day intervals. Safety and effectiveness have not been proven.

Children (under 18 years old)

There is not enough available evidence to recommend the use of shiitake in children.

Safety
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

Avoid if known allergy/hypersensitivity to shiitake mushrooms. Rash, toxic epidermal necrolysis, and photodermatitis may occur from contact or ingestion. Allergic contact dermatitis has been induced by shiitake hyphae (filaments). Mushroom workers exposed to shiitake spores by inhalation have experienced hypersensitivity pneumonitis. A case report exists of an anaphaylactoid (life-threatening) reaction in a patient with HIV who was taking lentinan.

Side Effects and Warnings

Most minor adverse effects are believed to be caused by lentinan, the polysaccharide derivative of shiitake. There has been one report each of depression, rigor, fever, chills, and abnormal blood cell counts (granulocytopenia); elevated liver enzymes were reported in one study following treatment with lentinan in cancer patients.

Shiitake can cause abdominal discomfort and abnormal blood cell counts (eosinophilia) when taken by mouth. Abdominal obstruction and death was reported due to the ingestion of a whole shiitake mushroom. Temporary diarrhea and abdominal bloating may occur after taking high amounts of shiitake.

Rapid intravenous infusion of lentinan, the polysaccharide derivative of shiitake, to advanced cancer patients was reported to cause anterior chest depression and dryness of the throat in one study; slow infusion relieved these symptoms.

Back pain and leg pain has been reported following the administration of lentinan in cancer patients.

Shiitake can cause "shiitake" dermatitis and possibly photosensitivity when taken by mouth. Allergic contact dermatitis has been induced by shiitake hyphae (filaments).

Pregnancy and Breastfeeding

Shiitake mushroom is not recommended in pregnant or breastfeeding women in medicinal amounts due to a lack of available scientific evidence.

Although not well studied in humans, lentinan and shiitake extracts may interact with antifungals, antivirals, antioxidants, and immunomodulators. Caution is advised.

Lentinan has been used as an adjunct with cancer therapies to prolong survival time and increase quality of life.

Based on preliminary animal study, shiitake may reduce blood levels of free cholesterol, triglycerides, and phospholipids.

In a laboratory study, essential oil from shiitake inhibited platelet aggregation and therefore may increase the risk of bleeding when taken with drugs that also increase bleeding risk like warfarin (Coumadin®) or ibuprofen (Advil®, Aleve®). Lentinan, the polysaccharide derivative of shiitake, may cause mildly abnormal blood cell counts (thrombocytopenia).

Lentinus edodes has been shown to inhibit cyclooxygenase activity in laboratory study and therefore may interact with drugs like Tylenol® or Celebrex®.

Mushroom polysaccharides, especially beta-glucans such as lentinan from Lentinus edodes, may interfere with the way the liver breaks down certain drugs (through the suppression of CYP1As). Consult a qualified healthcare professional, including a pharmacist, to check for interactions.

Lentinan may cause increased sun sensitivity that can be worsened by drugs like Retin-A® and tetracycline antibiotics.

Interactions with Herbs and Dietary Supplements

Although not well studied in humans, lentinan and shiitake extracts may interact with antifungals, antivirals, antioxidants, and immunomodulators. Caution is advised.

Based on preliminary animal study, shiitake may reduce blood levels of free cholesterol, triglycerides, and phospholipids.

In a laboratory study, essential oil from shiitake inhibited platelet aggregation and therefore may increase the risk of bleeding when taken with herbs or supplements that also increase bleeding risk like garlic or saw palmetto. Lentinan, the polysaccharide derivative of shiitake, may cause mildly abnormal blood cell counts (thrombocytopenia).

Mushroom polysaccharides, especially beta-glucans such as lentinan from Lentinus edodes, may interfere with the way the liver breaks down certain herbs and supplements (through suppression of CYP1As). Please check with a doctor and pharmacist to screen for potential interactions.

Lentinan may cause increased sun sensitivity that can be worsened by herbs and supplements like St. John's wort, or capsaicin.

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.